Comments from actual users of these phones would be far more informative. Karma to scott_karana for mentioning his experience with their version of Android.
MIUI is actually a fairly well-known (and used) Android variant. Fun fact: it was supposedly based on iOS' looks but branched off into their own direction after ICS. Since then, iOS 7 was (comically, IMO) compared to MIUI and people believed Apple was inspired by it. It was even sold on a phone that was very iPhone-esque: http://www.blogcdn.com/www.engadget.com/media/2011/08/xiaomi...